http://www.antoniocasella.eu/archipsy/Johns_2001.pdf

The continuity of psychotic experiences in the general population

https://www.bmj.com/content/bmj/1/5125/836.2.full.pdf

Dictionary of psychology

Background. The aims of the study were: first to examine, using clinical symptoms of patients as a template, whether the correlated but independent dimensions of positive, negative and depressive symptoms that have been identified in clinical psychosis, also have a distribution as non-clinical experiences in the general population; and second, to establish to what degree population variation in experience of positive and negative features of psychosis is actually independent of experience of depression. Method. In a representative population sample of 932 young men, we measured experiences of positive, negative and depressive features of psychosis, using a 40-item self-report instrument. Confirmatory factor analysis was used to compare the fit of hypothesized one-, two- and threefactor solutions. Results. A three-factor model of separate depressive, positive and negative dimensions provided a better fit to the data than either a two-factor or unidimensional model. All three dimensions were correlated with each other, but also showed good discriminant validity in relation to established scales, confirming their relative independence. Conclusion. The data suggest that the correlated dimensions of clinical psychosis also have a distribution in the general population, and that depressive symptoms may form an integral part of psychosis-like experiences in the general population.

/pdf/evidence-that-three-dimensions-of-psychosis-have-a-1l1kcpyqpl.pdf

Evidence that three dimensions of psychosis have a distribution in the general population.

A comprehensive evolutionary framework for understanding the maintenance of heritable behavioral variation in humans is yet to be developed. Some evolutionary psychologists have argued that heritable variation will not be found in important, fitness-relevant characteristics because of the winnowing effect of natural selection. This article propounds the opposite view. Heritable variation is ubiquitous in all species, and there are a number of frameworks for understanding its persistence. The author argues that each of the Big Five dimensions of human personality can be seen as the result of a trade-off between different fitness costs and benefits. As there is no unconditionally optimal value of these trade-offs, it is to be expected that genetic diversity will be retained in the population.

/pdf/the-evolution-of-personality-variation-in-humans-and-other-aiitzjz5h2.pdf

The Evolution of Personality Variation in Humans and Other Animals.

The Peters et al. Delusions Inventory (PDI) was designed to measure delusional ideation in the normal population, using the Present State Examination as a template. The multidimensionality of delusions was incorporated by assessing measures of distress, preoccupation, and conviction. Individual items were endorsed by one in four adults on average. No sex differences were found, and an inverse relationship with age was obtained. Good internal consistency was found, and its concurrent validity was confirmed by the percentages of common variance with three scales measuring schizotypy, magical ideation, and delusions. PDI scores up to 1 year later remained consistent, establishing its test-retest reliability. Psychotic inpatients had significantly higher scores, establishing its criterion validity. The ranges of scores between the normal and deluded groups overlapped considerably, consistent with the continuity view of psychosis. The two samples were differentiated by their ratings on the distress, preoccupation, and conviction scales, confirming the necessity for a multidimensional analysis of delusional thinking. Possible avenues of research using this scale and its clinical utility are highlighted.

/pdf/measurement-of-delusional-ideation-in-the-normal-population-4wp2j1r1pv.pdf

Measurement of Delusional Ideation in the Normal Population: Introducing the PDI (Peters et al. Delusions Inventory)

The heterogeneity of schizotypal traits, suggested in previous research, was further investigated in a sample of subjects (N = 1095) administered a composite questionnaire consisting of a large number of published scales the majority of which were designed to measure psychotic characteristics. Factor analysis confirmed the four components previously indicated in our work with the same instrument; namely, ‘aberrant perceptions and beliefs’, ‘cognitive disorganization’, ‘introvertive anhedonia’ and ‘asocial behaviour’. This structure was maintained regardless of whether or not the analysis included scales from the Eysenck Personality Questionnaire, which might otherwise have been held to explain the variance. ‘Aberrant perceptions and beliefs’—reminiscent of the positive symptoms of schizophrenia was the strongest component; but, given the multidimensional nature of the data, together with the pattern of factor loadings and intercorrelations for the scales involved, it was concluded that the broader term ‘psychosis-proneness’ or ‘psychoticism’ (in a non-Eysenckian sense) might be a better descriptor of the clinical and personality domain sampled.

Charles McCreery

Papers

The factor structure of "schizotypal' traits: a large replication study.

Healthy schizotypy: the case of out-of-the-body experiences

Out-of-the-body experiences and personality.

A study of hallucination in normal subjects—I. Self-report data

Hallucinations and arousability: Pointers to a theory of psychosis.